THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



JANUARY 1844. 



I. On the Action of Yellow Light in producing the Green Colour, 

 and Indigo Light the Movements of Plants. By D. P. 

 Gardner, M.D., Corresponding Member of the Lyceum of 

 Natural History, New York*. 



1. rpHE object of this paper is to prove the existence of 

 ■L different properties in the rays of the spectrum, iu 

 their action on vegetables ; and more especially to show that 

 the rays which produce the green colour of plants are alto- 

 gether dissimilar from those which influence their movements 

 towards light; the colour being developed by the less re- 

 frangible rays, and chiefly by the yellow; whereas the motion 

 is influenced by indigo light. The discussion of the subject 

 will be divided under three heads: — 



1st. On the Production of Chlorophyl by yellow light. 



2nd. On the Movements of Plants towards indigo light. 



3rd. Some applications of these facts to vegetable physiology. 



Part I. On the Production of Chlorophyl by yellow light. 



2. It is a fundamental fact in botany that light is necessary 

 to the formation of chlorophyl. Von Humboldt adduced cer- 

 tain exceptions to this law, in the case of plants found in the 

 mines of Freyberg, and with Senebier ascribed the green 

 matter to the action of hydrogen gas. But the experiments 

 of the latter have failed in the hands of DeCandolle, and a 

 series instituted by myself, and conducted with great care, 

 were equally unsuccessful. On the other hand, .Humboldt 

 succeeded in greening a plant of Lepidium sativum, raised in 

 darkness, by the light of two lamps, and DeCandolle obtained 

 the same result with six Argand lamps. 



3. The investigation has been subsequently confined to the 

 name of the ray which produces the chlorophyl. Formerly 

 it was tacitly admitted that the chemical or blue ray was most 



* Communicated by the Author. 

 Phil. Mag. S. 3. Vol.24. No. 156. Jan. 1844. B 



